Internet DRAFT - draft-huang-computing-delivery-in-routing-network
draft-huang-computing-delivery-in-routing-network
RTGWG D.H. Daniel
Internet-Draft B.T. Bin
Intended status: Standards Track ZTE Corporation
Expires: 8 September 2022 P.L. Peng
China Mobile
7 March 2022
Computing Delivery in Routing Network
draft-huang-computing-delivery-in-routing-network-01
Abstract
This document drafts a proposal of the architecture of Computing
Delivery in Routing Network which incorporates both computing and
networking metrics into the routing polices and enables the network
sensing and scheduling computing services based upon traditional
networking services. A mechanism of two-class computing status
granularity and two segment routing is illustrated for end-to-end
networking and computing service in the cloud sites, while major
networking and computing actors is defined in terms of functionality.
An example work flow is demonstrated, and both control plane and data
plane solution consideration is proposed..
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Computing delivery in routing network reference
architecture . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Hierarchical granularity routing scheme . . . . . . . . . 5
3.2. Two-segment routing and forwarding . . . . . . . . . . . 6
3.3. Cross-domain computing routing and forwarding . . . . . . 6
3.4. CSI routing . . . . . . . . . . . . . . . . . . . . . . . 7
3.5. Traffic affinity . . . . . . . . . . . . . . . . . . . . 7
4. Computing delivery in routing network architecture work
flow . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Computing resource and service update work flow . . . . . 8
4.2. Service flow routing and forwarding work flow . . . . . . 8
5. Control plane . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Centralized control plane . . . . . . . . . . . . . . . . 9
5.2. Distributed control plane . . . . . . . . . . . . . . . . 9
5.3. Hybrid control plane . . . . . . . . . . . . . . . . . . 9
6. Data plane . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. CSI encapsulation . . . . . . . . . . . . . . . . . . . . 10
6.2. CSI for GCR, CUR and LCR . . . . . . . . . . . . . . . . 10
7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Security Considerations . . . . . . . . . . . . . . . . . . . 11
11. Informative References . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Computing-related services have been provided in such a way that
computing resources either are confined within isolated sites (data
centers, MECs etc.) without coordination among multiple sites or they
are coordinated and managed within specific and closed service
systems without fine-grained networking facilitation, while the
industry develops into an era in which the computing resources start
migrating from centralized data centers to distributed edge nodes.
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Therefore substantial benefits in light of both cost and efficiency
resulting from scale of economy, would be brought into multiple
industries by intelligently and dynamically connecting the
distributed computing resources and rendering the coordinated
computing resources as a unified and virtual resource pool. On top
of the cost and efficiency gains, applications as well as services
would be served in a more sophisticated way in which computing and
networking resources could be aligned more efficiently and agilely
than conventional way in which the two are delivered in separate
systems. Some impressive drafts such as
[I-D.liu-dyncast-ps-usecases] and [I-D.li-dyncast-architecture]
analyze the benefits of routing related solution, and give the
reference architecture and preliminary test results. End
applications could be served not only by fine-grained computing
services but also fine-grained networking services rather than the
best-effort networking services without routing network involved
otherwise. The cost is the burden of maintaining and sensing
computing resource status in the networking layer. The architecture
proposal is designed to be as much smoothly compatible with the
ongoing routing architecture as possible.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Terminology
* Global Computing-related Routing Node (GCR): routing node
maintaining computing resource as well as service status from
remote cloud sites, and executing the cross-site routing policies
in terms of the aforementioned status as well as the
identification of computing resource and service. GCR usually
resides at the network edge and works as ingress of the end to end
service flow.
* Local Computing-related Routing Node (LCR): routing node
maintaining computing resource as well as service status from the
geographically local cloud sites and being responsible for the
last hop of the service flow towards the computing resource and
service instance in the specific cloud site. LCAT usually resides
at the network edge and works as egress of the end to end service
flow.
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* Computing Unaware Routing Node (CUR): routing node unaware of
computing resource and service status and disregarding
encapsulation of the identification of computing service. CUR
usually resides between GCR and LCR and works as ordinary routing
nodes and stays irrelevant of computing delivery.
* Global Computing Resource and Service Status (GCRS): General cloud
site status of the computing resource and service which consists
of overall resource occupation and types of computing service
(algorithms, functions etc.) the specific cloud site provides.
GCRS is maintained at GCR and expected to remain relatively stable
and change in slow frequency.
* Local Computing Resource and Service Status (LCRS): fine-grained
cloud site status of the computing resource and service which
consists of status of each active computing service instance as
well as its parameters which impact the way the instance would be
selected and visited by LCR. LCRS is maintained at LCR and
expected to stay quite active and change in high frequency.
* Computing Service Identification (CSI): a globally unique
identification of a computing service with optional parameters,
and it could be an IPv6-like address or specifically designed
identification structure.
* Instantiated Computing Service (ICS): an active instance of a
computing service identification which resides in a host usually
purporting to a server, container or virtual machine.
3. Computing delivery in routing network reference architecture
Routing network is enabled sensing the computing resource and service
from the cloud sites and routing the service flow according to both
network and computing metrics by a computing delivery in routing
network architecture as illustrated in figure 1. The architecture is
a horizontal convergence of cloud and network, while the latter
maintains the converged resource status and thus is able to achieve
an end to end routing and forwarding policy from a perspective of
cloud and network resource. PE1 maintains GCRS with a whole picture
of the multiple cloud sites, and executes the routing policy for the
network segment between PE1 and PE2 or PE3, namely between ingress
and egress, while PE2 maintains LCRS with a focus picture of the
cloud site where S1 resides, and establishes a connection towards S1.
S1 is an active instance of a specific computing service type (CSI).
On top of the role of LCR which maintains LCRS, PE2 and PE3 also
fulfill the role GCR which maintains GCRS from neighboring cloud
sites. P provides traditional routing and forwarding functionality
for computing service flow, and remains unaware of any computing-
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related status as well as CSI encapsulations.
+--------+ +--------+
+------>|LCR/GCR |------->| ICS |
| +--------+ +--------+
+--------+ +--------+ | PE2 S1
| GCR |--->| CUR |--+
+--------+ +--------+ | PE3 S2
PE1 P | +--------+ +--------+
+------>|LCR/GCR |------->| ICS |
+--------+ +--------+
|<------------ Network domain --------------->|<--Computing->|
domain
Figure 1
3.1. Hierarchical granularity routing scheme
Status updates of computing resource and service in the cloud sites
extend in a quite broad range from relatively stable service types
and overall resource occupation to extremely dynamic capacity changes
as well as busy and idle cycle of service instance. It would be a
disaster to build all of the status updates in the network layer
which would bring overburdened and volatile routing tables.
It should be reasonable to divide the wide range of computing
resource and services into different categories with differentiated
characteristics from routing perspective. GCRS and LCRS correspond
to cross-site domain and local site domain respectively, and GCRS
aggregates the computing resource and service status with low update
frequency from multiple cloud sites while LCRS focuses only upon the
status with high frequency in the local sites. Under this two-
granularity scheme, computing-related routing table of GCRS in the
GCR remains in a position roughly as stable as the traditional
routing table, and the LCRS in the LCR maintains a near synchronized
state table of the highly dynamic updates of computing service
instances in the local cloud site. Nonetheless, LCRS focusing upon a
single and local cloud site is the normal case while upon multiple
sites should be exemption if not impossible.
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3.2. Two-segment routing and forwarding
When it comes to end to end service flow routing and forwarding,
there is an status information gap between GCRS and LCRS, therefore a
two-segment mechanism has to be in place in line with the two-
granularity routing scheme demonstrated in 3.1. As is illustrated in
figure 2, R1as ingress determines the specific service flow's egress
which turns out to be R2 according to policy calculation from GCRS.
In particular, the CSI from both in-band (user plane) and out-band
(control plane) is the only index for R1 to calculate and determine
the egress, it's highly possible to make this egress calculation in
terms of both networking (bandwidth, latency etc) and computing
Service Agreement Level. Nevertheless, the two SLA routing
optimization could be decoupled to such a degree that the traditional
routing algorithms could remain as they are. The convergence of the
SLA policies as well as the methods to make GCR aware of the two SLA
is out of scope of this proposal.
+--------+ +--------+ +--------+ +--------+
| GCRS |--->| |--->| LCRS |--->| ICS |
+--------+ +--------+ +--------+ +--------+
R1 R
|<---------- GCRS segment ---------->|<- LCRS ->|
segment
Figure 2
When the service flow arrives at R2 which terminates the GCRS segment
routing and determines S1 which is the service instance selected
according to LCRS maintained at R2. Again CSI is the only index for
LCRS segment routing process.
3.3. Cross-domain computing routing and forwarding
Co-ordinated computing resource scheduling among multiple regions
which are usually connected by multiple network domains, as
illustrated in section 1, is an important part of intended scenarios
with regard to why computing-based scheduling and routing is proposed
in the first place. The two-segment routing and forwarding scheme
illustrated in 3.2 is a typical use case of cross-domain computing
routing and forwarding and a good building block for the full-domain
scenario solution. Computing metric information is brought into
network domain to enable the latter scheduling routing policies
beyond network. However, a particular scheme has to be put in place
to ensure mild and acceptable impacts upon the ongoing IP routing
scheme. A consistent CSI across terminal, network (multiple domains)
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and cloud along with hierarchical CSI-associated computing resource
and service status which corresponds with different network domains,
is the enhanced full-domain routing and forwarding solution. Each
domain maintains a corresponding computing resource and service
status at its edge node and makes the computing-based routing for the
domain-related segment which should be connected by the neighboring
segments.
3.4. CSI routing
CSI encapsulated in the headers and maintained in LCRS and GCRS
indicates an abstract service type rather than a geographically
explicit destination label, thus the routing scheme based upon CSI is
actually a two-part and two-layer process in which CSI only indicates
the routing intention of user's requested computing service type
where routing does not actually materialize in forwarding plane and
the explicit routing destination would be determined by LCRS and
GCRS. Therefore the actual routing falls within the traditional
routing scheme which remains intact.
Apart from the indication of computing service routing intention, CSI
could also indicates a specific network serivice requirements by
associating the networking service policy in GCRS which would
therefore schedule the network resources such as an SR tunnel,
guaranteed bandwidth etc. at egress.
Therefore, GCRS and LCRS in control plane along with CSI
encapsulation in user plane enables an logical computing routing sub-
layer which is able to be aware of the computing from cloud sites and
forward the service flow in terms of computing services as well as
computing resources. Nevertheless, this logical sub-layer remains
only relevant at ingress and egress nodes and is simply about
computing nodes selection rather than executing the real forwarding
and routing actions.
3.5. Traffic affinity
CSI holds the only semantics of the service type that could be
deployed as multiple instances within specific cloud site or across
multiple cloud sites, CSI in the destination field is not explicit
enough for all of the service flow packets to be forwarded to a
specific destination. Traffic affinity has to be guaranteed at both
GCR and LCR. Once the egress is determined at GCR, the binding
relationship between the egress and the service flow's unique
identification (5-tuple or other specifically designed labels) is
maintained and the subsequent flow could be forwarded upon this
binding table. Likewise LCR maintains the binding relationship
between the service flow identification and the selected service
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instance.
Traffic affinity could be guaranteed by mechanisms beyond routing
layer, but they will not be in the scope of this proposal.
4. Computing delivery in routing network architecture work flow
4.1. Computing resource and service update work flow
The full range of computing resource and service status from a
specific cloud site is registered at LCR which maintains LCRS in
itself and notifies the part of GCRS to remote GCRs where GCRS would
be thus maintained and updated. As is illustrated in figure 3,GCR in
R1 from site1 and site 2 is updated by R2 and R3, while LCRS of site
1 in R2 is updated by S1 and LCRS of site 2 in R3 is updated by S2.
GCRS in R2 and R3 is updated by each other. Edge routers associating
with local cloud site establish a mesh fabric to update the according
GCRS among the whole network domain, the computing resource and
services in distributed cloud sites thus are connected and could be
utilized as a single pool for the applications rather than the
isolated islands.
+--------+ +--------+
+---------------------------|LCR/GCR |<-------| ICS |
| +--------+ +--------+
+-----V--+ +--------+ A R2 | S1
| GCR | | CUR | | |
+-----A--+ +--------+ | R3 V S2
R1 | R +--------+ +--------+
+---------------------------|LCR/GCR |<-------| ICS |
+--------+ +--------+
|<--------- GCRS update domain ----------->|<-----LCRS------>|
domain
Figure 3
4.2. Service flow routing and forwarding work flow
From perspective of the service work flow, more details have actually
been demonstrated in 3.2 and 3.3. Rather than the traditional
destination-oriented routing mechanism and the segment routing in
which the ingress router is explicitly aware of a specific
destination, CSI as an abstract label without semantics of physical
address works as the required destination from viewpoint of the user
in computing delivery in routing network architecture. Therefore the
service flow has to be routed and forwarded segment by segment in
which the two segment destinations are determined by GCRS and LCRS
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respectively.
5. Control plane
5.1. Centralized control plane
LCRS's volatility makes it infeasible to be maintained and controlled
in a centralized entity, GCRS is the chief computing resource and
service status information to be collected and managed in the
controller when it comes to centralized control plane with regard to
computing delivery in routing network architecture. Routing and
forwarding policies from GCRS calculated in the centralized
controller, as is demonstrated in 3.2, apply only to the segment from
ingress and egress, while the second segment routing policy from
egress to the selected service instance in the cloud site is
determined by LCRS at egress.
Hierarchically centralized control plane architecture would be
strongly recommended under the circumstances of nationwide network
and cloud management.
5.2. Distributed control plane
GCRS is updated among the edge routers which have been connected in a
mesh way that each pair of edge routers could exchange GCRS to each
other, while LCRS will be unidirectionally updated from cloud site to
the associated edge router in which LCRS is maintained and its update
process is terminated.
Protocol consideration upon which GCRS and LCRS is updated is out of
the scope of this proposal and will be illustrated in another draft.
5.3. Hybrid control plane
It should be more efficient to update the GCRS by a distributed way
than a centralized way in terms of routing request and response in a
limited network and cloud domain, but be the opposite case in a
nationwide circumstance. This is how hybrid control plane could be
deployed in such a scheme that overall optimization is achieved.
6. Data plane
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6.1. CSI encapsulation
Computing service identification is the predominant index across the
entire computing delivery in routing network architecture under which
a new virtual routing sub-layer is employed with CSI working as the
virtual destination. Data plane indicates the routing and forwarding
orientation with CSI by inquiring GCRS and LCRS at GCR and LCR
respectively. CSI encapsulation could be achieved by extending the
existing packet header and also achieved by designing a dedicated
shim layer, which along with the specific structure of CSI are out of
the scope of this proposal and will be illustrated in another draft.
6.2. CSI for GCR, CUR and LCR
GCR encapsulates CSI in a designated header format as a proxy by
translating the user-originated CSI format, and makes the first
segment routing policy and starts routing and forwarding the service
traffic. CUR ignores CSI and simply forwards the traffic as usual.
LCR decapsulates CSI and makes the second segment routing policy and
completes the last hop routing and forwarding.
7. Summary
It would significantly benefit the industry by connecting and
coordinating the distributed computing resources and services and
more so by further converging networking and computing resource.
Uncertainty and the potential impacts over the ongoing network
architecture is the main reason for the community to think twice. By
classifying the end to end routing and forwarding path into two
segments, the impacts from computing status and metrics are to be
reduced to a degree they would be as acceptable and comfortable
enough as they are as networking status and metrics. In particular,
employment of CSI in computing delivery in routing network
architecture enables a new service routing possibility perfectly
compatible with the ongoing routing architecture.
8. Acknowledgements
To be added upon contributions, comments and suggestions.
9. IANA Considerations
This memo includes no request to IANA.
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10. Security Considerations
As information originated from the third party (cloud sites), both
GCRS and LCRS would be frequently updated in the network domain, both
security threats against the routing mechanisms and credibility and
security issues of the computing services should be taken into
account by architecture designing. The detailed analysis as well as
solution consideration will be proposed in the updated version of the
draft.
11. Informative References
[I-D.li-dyncast-architecture]
Li, Y., "Dynamic-Anycast Architecture", February 2021,
<https://datatracker.ietf.org/doc/draft-li-dyncast-
architecture/>.
[I-D.liu-dyncast-ps-usecases]
Liu, Peng., "Dynamic-Anycast (Dyncast) Use Cases and
Problem Statement", February 2021,
<https://datatracker.ietf.org/doc/draft-liu-dyncast-ps-
usecases/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Authors' Addresses
Daniel Huang
ZTE Corporation
Nanjing
Phone: +86 13770311052
Email: huang.guangping@zte.com.cn
Bin Tan
ZTE Corporation
Nanjing
Phone: +86 13918622159
Email: tan.bin@zte.com.cn
Peng Liu
China Mobile
Beijing
Phone: +86 13810146105
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Email: liupengyjy@chinamobile.com
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